把十六进制的颜色转换成十六进制的UIColor颜色
新建UIColor的分类，添加类方法；
在需要用到的地方导入头文件就可；
使用方法：self.view.backgroundColor=[UIColor colorWithRGB:@"#81c52b"];
<pre>
+(UIColor*)colorWithhexString:(NSString *)hexString
{
NSString *cString = [[hexString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]uppercaseString];//字符串处理
//例子，stringToConvert #ffffff
if ([cString length] <6)
return [UIColor whiteColor];//如果非十六进制，返回白色
if ([cString hasPrefix:@"#"])
cString = [cString substringFromIndex:1];//去掉头
if ([cString length] !=6)//去头非十六进制，返回白色
return [UIColor whiteColor];
//分别取RGB的值
NSRange range;
range.location =0;
range.length =2;
NSString *rString = [cString substringWithRange:range];
range.location =2;
NSString *gString = [cString substringWithRange:range];
range.location =4;
NSString *bString = [cString substringWithRange:range];
unsigned int r, g, b;
//NSScanner把扫描出的制定的字符串转换成Int类型
[[NSScanner scannerWithString:rString] scanHexInt:&r];
[[NSScanner scannerWithString:gString] scanHexInt:&g];
[[NSScanner scannerWithString:bString] scanHexInt:&b];
//转换为UIColor
return [UIColor colorWithRed:((float) r /255.0f)
green:((float) g /255.0f)
blue:((float) b /255.0f)
alpha:1.0f];
}
</pre>
